The present invention relates to N-(phenylsulfonyl)-picolinamide derivatives, a process for producing the same and a herbicide comprising said derivatives as an active ingredient.
The following N-(phenylsulfonyl)picolinamide derivatives have been known heretofore.
N-[(4-Methylphenyl)sulfonyl]picolinamide (U.S. Pat. No. 5,294,610).
N-[(4-Aminophenyl)sulfonyl]picolinamide.
There is however no report that N-(phenylsulfonyl)-picolinamide derivatives can be used as an effective ingredient of herbicides.
By the way, there have conventionally been strong demands for herbicides capable of exhibiting excellent herbicidal activity even at such low application dosages as bringing about advantage of reducing the amount present in the environment, herbicides capable of exhibiting selectivity between crops and weeds irrespective of variations in environmental conditions, herbicides free from crop injury to the second crop in double-cropping, etc.
The present invention has been completed with a view toward meeting such demands as described above.
Accordingly, objects of the present invention are to provide novel compounds exhibiting excellent herbicidal effect, processes for producing the same, and novel herbicides comprising the same compound as the active ingredient.
As the result of various studies in order to find N-(phenylsulfonyl)picolinamide derivatives industrially effective, the present inventors have found that N-(phenylsulfonyl)-picolinamide derivatives have high herbicidal effect, and thus the present invention has been completed.
The present invention has the following constituent features.
The first invention relates to a herbicide comprising an N-(phenylsulfonyl)picolinamide derivative of the following formula (I) as the active ingredient: 
wherein X represents halogen atom, C1-C4 alkyl group, C1-C4 haloalkyl group, C1-C4 alkoxy group, C1-C4 haloalkoxy group, (C1-C4 alkoxy)carbonyl group, (di-C1-C4 alkylamino)sulfonyl group, [Nxe2x80x94(C1-C4 alkyl)-Nxe2x80x94(C1-C4 alkoxy)amino]sulfonyl group, (C1-C4 alkylamino)sulfonyl group, C1-C4 alkylthio group, C1-C4 alkylsulfinyl group, C1-C4 alkylsulfonyl group or nitro group,
n is an integer of 0-5. In case of n being 2 or more, each X may be identical or different,
Y represents halogen atom, C1-C4 alkyl group, C1-C4 haloalkyl group, C1-C4 alkoxy group, C1-C4 haloalkoxy group, C1-C4 alkylthio group, C1-C4 haloalkylthio group, amino group, C1-C4 alkylamino group, di-C1-C4 alkylamino group, (C1-C4 alkoxy) C1-C4 alkyl group, (C1-C4 alkylthio) C1-C4 alkyl group or nitro group,
m is an integer of 0-4, and each Y may be identical or different in case of m being 2 or more.
The second invention relates to a process for producing an N-(phenylsulfonyl)picolinamide derivative of the following formula (I) which comprises condensing a substituted picolinic acid of the formula (II) with a substituted benzenesulfonamide of the formula (III) under dehydration, which is shown in the following reaction formula (The first process for production): 
wherein X, Y, n and m are each the same definition as described above.
The third invention relates to a process for producing an N-(phenylsulfonyl)picolinamide derivative of the formula (I) which comprises reacting a substituted picolinic phenyl ester of the formula (IV) with a substituted benzenesulfonamide of the formula (III) in the presence of a basic compound, which is shown in the following reaction formula (the second process for production). 
wherein X, Y, n and m are each the same definition as described above,
Z represents halogen atom, C1-C4 alkyl group, C1-C4 alkoxy group or nitro group, s is an integer of 0-5, and each Z may be identical or different in case of s being 2 or more.
The fourth invention relates to an N-(phenylsulfonyl)-picolinamide derivative of the following formula (I): 
wherein X, Y, n and m are each the same definition as described above, exclusive of N-[(4-methylphenyl)sulfonyl]picolinamide.
The present invention will be illustrated in detail in the following.
The groups X and Y of the N-(phenylsulfonyl)picolinamide derivatives of the above-described formula (I) according to the present invention include the following typical substituents, and n and m are preferred to be the following values.
Regarding X:
Fluorine atom, chlorine atom and bromine atom as the halogen atom.
Methyl group as the C1-C4 alkyl group.
Trifluoromethyl group as the C1-C4 haloalkyl group.
Methoxy group as the C1-C4 alkoxy group.
Trifluoromethoxy group as the C1-C4 haloalkoxy group.
Methoxycarbonyl group as the (C1-C4 alkoxy)carbonyl group.
(Dimethylamino)sulfonyl group, (diethylamino)sulfonyl group and (methylethylamino)sulfonyl group as the (di-C1-C4 alkylamino)sulfonyl group. In this case, each C1-C4 alkyl may be identical or different.
(N-Methyl-N-methoxyamino)sulfonyl group as the [Nxe2x80x94(C1-C4 alkyl)-Nxe2x80x94(C1-C4 alkoxy)amino]sulfonyl group.
Methylaminosulfonyl group as the (C1-C4 alkylamino)-sulfonyl group.
Methylthio group as the C1-C4 alkylthio group.
Methylsulfinyl group as the C1-C4 alkylsulfinyl group.
Methylsulfonyl group as the C1-C4 alkylsulfonyl group.
Preferred examples of these groups include fluorine atom, chlorine atom, methyl group, trifluoromethyl group, methoxy group, trifluoromethoxy group, methoxycarbonyl group, (dimethylamino)-sulfonyl group, (N-methyl-N-methoxyamino)sulfonyl group, methylthio group, methylsulfinyl group and methylsulfonyl group.
A preferred range of n is 0 to 3, more preferably 0 to 2.
Since the preferred positions of X attached to the benzene ring are ortho positions to the N-substituted sulfamoyl group, it is preferred that the X attaches to one or both of them.
Regarding Ym:
Fluorine atom, chlorine atom and bromine atom as the halogen atom.
Methyl group, ethyl group and 1-methylethyl group as the C1-C4 alkyl group.
Fluoromethyl group, difluroromethyl group and trifluoromethyl group as the C1-C4 haloalkyl group.
Methoxy group, ethoxy group and (1-methylethyl)oxy group as the C1-C4 alkoxy group.
Difluoromethoxy group, trifluoromethoxy group, (2-fluoroethyl)oxy group, (2,2-difluoroethyl)oxy group, (2,2,2-trifluoroethyl)oxy group, (1,1,2,2-tetrafuruoroethyl)oxy group, (2-chloro-1,1,2-trifluoroethyl)oxy group and (3,3,3-trifluroropropyl)oxy group as the C1-C4 haloalkoxy group.
Methylthio group as the C1-C4 alkylthio group.
Difluoromethylthio group as the C1-C4 haloalkylthio group.
Methylamino group as the C1-C4 alkylamino group.
Dimethylamino group and methyl ethyl amino group. In this case, each C1-C4 alkyl may be identical or different.
Methoxymethyl group as (C1-C4 alkoxy) C1-C4 alkyl group.
Methylthiomethyl group as the (C1-C4 alkylthio) C1-C4 alkyl group.
Preferred examples of these groups include fluorine atom, chlorine atom, bromine atom, methyl group, 1-methylethyl group, fluoromethyl group, trifluoromethyl group, methoxy group, ethoxy group, (1-methylethyl)oxy group, difluoromethoxy group, trifluoromethoxy group, methylthio group, difluoromethylthio group, methylamino group, dimethylamino group, etc.
A preferred range of m is 0 to 3, more preferably 0 to 2.
Since the preferred positions of Y attached to the pyridine ring are 4-, 5-and 6-positions when the nitrogen atom of the pyridine ring is 1-position and the N-substituted carbamoyl group is 2-position, Y is preferred to be attached to at least one of them.
Specific examples of the N-(phenylsulfonyl)picolinamide derivatives of the above described formula (I) according to the present invention include those as shown in Table 1.
The columns of substituent Xn and Ym in the Table 1 have the following common rule.
Xn: xe2x80x9cposition-substituentxe2x80x9d is described as the case that the N-substituted sulfamoyl group on the benzene ring is I-position.
Accordingly, xe2x80x9c2-CF3xe2x80x9d means that the CF3 is attached to 2-position.
Similarly, xe2x80x9c2-COOCH3xe2x80x9d means that the COOCH3 is attached to 2-position, and xe2x80x9c2-Clxe2x80x9d means that a chlorine atom is attached to 2-position. These cases correspond to n being 1.
xe2x80x9c2,4-Cl2xe2x80x9d means that each chlorine atom is attached to 2- and 4-positions. Similarly, xe2x80x9c2,6-F2xe2x80x9d means that each fluorine atom is attached to 2- and 6-positions. These cases correspond to n being 2.
Ym: xe2x80x9cposition-substituentxe2x80x9d is described as the case that the N-substituted carbamoyl group on the pyridine ring is 2-position.
Accordingly, xe2x80x9c4-OCH3xe2x80x9d means that the OCH3 is attached to 4-position. This case corresponds to m being 1.
xe2x80x9c4,6-Cl2xe2x80x9d means that each chlorine atom is attached to 4- and 6-positions. Similarly, xe2x80x9c4,6-(OCH3)2xe2x80x9d means that each OCH3 is attached to 4- and 6-positions. These cases correspond to m being 2.
xe2x80x9c4-OCH36-Clxe2x80x9d means that OCH3 is attached to 4-position and the chlorine is attached to 6-position. This case corresponds to m being 2.
Xn of substituted benzenesulfonamide of the formula (III) shown in Table 3 and Ym of substituted picolinic acid of the formula (II) in Table 2 follows the same rule as described above. The same rule is used in this description, too.
In the first and the second processes according to the present invention, one or more of the following solvents can be used in the reaction steps and the step for isolation of the product.
Aromatic hydrocarbons such as benzene, toluene, xylene, methylnaphthalene, etc.
Aliphatic hydrocarbons such as petroleum ether, pentane, hexane, heptane, methylcyclohexane, etc.
Chlorinated hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, 1,2-dichloroethane, tetrachloroethane, chlorobenzene, etc.
Amides such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidinone, etc.
Ethers such as diethyl ether, dimethoxyethane, diisopropyl ether, tetrahydrofuran, diglyme, dioxane, etc.
Lower alkyl alcohols such as methyl alcohol, ethyl alcohol, 1-methyl alcohol, 1,1-dimethylethyl alcohol, etc.
The other solvents such as water, carbondioxide, acetonitrile, nitromethane, ethyl acetate, acetic acid, propionic acid, pyridine, methylsulfoxide, hexamethyl phosphoric amide, etc.
Reactions of the first and the second processes according to the present invention are preferably carried out in a solvent or a solvent mixture. It is possible for the reactions to use a solvent composition consisting of solvents which do not form a homogeneous phase one another. In such a case, it is suitable to add to the reaction system a phase-transfer catalyst, for example, common quaternary ammonium salt or crown ether.
When it is desired to use a salt in the reaction step or the step for separation of the product, one or more of the following salts can be used in the present invention.
Alkali metals such as lithium, sodium, potassium, etc., and alkaline earth metals such as magnesium, etc.
Alkali metal alkoxides such as sodium methoxide, sodium ethoxide, potassium t-butoxide, etc.
Alkali metal hydrides such as sodium hydride, potassium hydride, etc.
Alkali metal hydrogencarbonate such as potassium hydrogencarbonate, sodium hydrogencarbonate, etc.
Alkali metal hydroxide such as sodium hydroxide, potassium hydroxide, etc.
Alkaline earth metal hydroxide such as magnesium hydroxide, calcium hydroxide, etc.
Alkaline earth metal oxides such as magnesium oxide, calcium oxide, etc.
Alkali metal carbonates such as potassium carbonate, sodium carbonate, etc.
Alkaline earth metal hydrides such as calcium hydride, etc.
Organometallic compounds of alkali metal such as methyllithium, ethyllithium, butyllithium, sec-butyllithium, tert-butyllithium, phenyllithium, etc.
Organic Grignard reagents such as methylmagnesium iodide, ethylmagnesium bromide, n-butylmagnesium bromide, etc.
Organocopper compounds prepared from an organometallic compound of alkali metal or a Grignard reagent and a monovalent copper salt.
Alkali metal amides such as lithium diisopropylamide, etc.
Organic amines such as triethylamine, pyridine, 4-dimethylaminopyridine, N,N-dimethylaniline, 1,8-diazabicyclo[5.4.0]undeca-7-ene (referred as DBU, hereinafter)
When it is desired to use an acid in the reaction step or the step for separation of the product, one or more of the following acids can be used in the present invention.
Inorganic acids such as hydrochloric acid, hydrobromic acid, hydroiodic acid, perchloric acid, sulfuric acid, etc.; organic acids such as formic acid, acetic acid, butyric acid, p-toluenesulfonic acid, etc.; and Lewis acid such as boron trifluoride, aluminum chloride, zinc chloride, etc.
The N-(phenylsulfonyl)picolinamide derivatives of the above formula (I) according to the present invention can be produced by condensation reaction of 1 mol of a substituted picolinic acid of the above formula (II) with 0.7-1.5 equivalents of a substituted benzenesulfonamide of the above formula (III) under dehydration.
(The First Process for Production)
Upon the condensation reaction under dehydration in the above process for production, 1,3-dicyclohexylcarbodiimide, diethyl cyanophosphate, 1,1xe2x80x2-carbonyldiimidazole, thionyl chloride, etc are used generally as the dehydration-condensation agent, and chlorinated hydrocarbons such as methylene chloride, chloroform, 1,2-dichloroethane, etc. and ethers such as diethyl ether, tetrahydrofuran, dioxane, etc. are used generally as the solvent. Preferably, 1,3-dicyclohexylcarbodiimide is used as the dehydration-condensation agent and dichloromethane, tetrahydrofuran or dioxane is used as the solvent.
In the above described process for production, the substituted benzenesulfonamide of the above formula (III) and the substituted picolinic acid of the above formula (II) are mixed with the dehydration-condensation agent and the solvent, and the mixture was generally allowed to react at a temperature of 0-30xc2x0 C., and preferably at 0-5xc2x0 C. and then at 15-30xc2x0 C. The reaction period of time is 1-6 hours and preferably 3-4 hours. This reaction is advantageously carried out in the presence of 4-dimethylaminopyridine.
The N-(phenylsulfonyl)picolinamide derivatives of the above formula (I) according to the present invention can be produced by reacting a substituted picolinic acid phenyl ester of the above formula (IV) with a substituted benzenesulfonamide of the formula (III) in a solvent, preferably in an aprotic polar solvent in the presence of a basic compound. (The second process for production)
This process is suitable in case of using a substituted compound in which substituents in ortho positions of the sulfamoyl group on the benzene ring do not cause ring-closure condensation with the sulfamoyl group under a basic condition. Such substituents include halogen atoms, C1-C4 alkyl groups, C1-C4 haloalkyl groups, C1-C4 alkoxy groups, C1-C4 haloalkoxy groups, (di-C1-C4 alkylamino)sulfonyl groups, [Nxe2x80x94(C1-C4 alkyl)-Nxe2x80x94(C1-C4 alkoxy)amino]sulfonyl groups, (C1-C4 alkylamino)sulfonyl groups, C1-C4 alkylthio groups, C1-C4 alkylsulfonyl groups and nitro group.
Specific examples of the substituents Xn include 2-CF3, 2-CH3, 2,3-Cl2, 2,4-Cl2 2,5-Cl2 2,6-Cl2 2-Cl, 2-OCF3, 2-SO2N(CH3)2, 2-SO2N(CH2CH3)2, 2-SO2N(OCH3)(CH3), 2,6-F2, 2-SO2NHCH3, 2-SCH3 and 2-SO2CH3.
The above mentioned reaction step is preferred to carry out in an inert organic solvent, for example, hydrocarbon such as benzene, toluene, xylene or cyclohexane, chlorinated hydrocarbon such as methylene chloride, chloroform, carbon tetrachloride or chlorobenzene, or ether such as diethyl ether, dimethoxyethane, diethylene glycol, dimethyl ether, tetrahydrofuran or dioxane, or in an aprotic polar solvent such as acetonitrile, nitromethane, N,N-dimethylformamide, N,N-dimethylacetamide or methylsulfoxide, and preferably, N,N-dimethylformamide or N,N-dimethylacetamide, at temperature of xe2x88x9210-160xc2x0 C., preferably 20-100xc2x0 C. In this reaction, sodium hydride or DBU is preferably used as the basic compound. Further, the reaction period of time is 1-5 hours, and preferably 1.5-2.5 hours.
The substituted picolinic acid of the formula (II) used in the first process for producing the N-(phenylsulfonyl)picolinamide of the formula (I) according to the present invention are listed in Table 2. It is possible to derive from these compounds the substituted picolinic acid phenyl esters of the formula (IV) used as the starting material in the second process according to the present invention.
In the following, starting materials used in the present invention will be illustrated in detail.
The substituted picolinic acid of the formula (II) and the substituted picolinic acid lower alkyl ester of the following formula (V) which is the starting material thereof can be synthesized according to the following reactions (1)-(3), whereby the carboxyl group or the lower alkoxycarbonyl group can be formed on the 2-position of the pyridine ring. 
wherein Y is halogen atom, C1-C4 alkyl group, C1-C4 haloalkyl group, C1-C4 alkoxy group, C1-C4 haloalkoxy group, C1-C4 alkylthio group, C1-C4 haloalkylthio group, amino group, C1-C4 alkylamino group, di-C1-C4 alkylamino group, (C1-C4 alkoxy) C1-C4 alkyl group, (C1-C4 alkylthio) C1-C4 alkyl group or nitro group,
m is an integer of 0-4, and each Y may be identical or different in case of m being 2 or more, and
R1 represents C1-C4 alkyl group.
(1) Substituted picolinic acid lower alkyl ester having a lower alkoxycarbonyl group derived from hydroxycarbonyl group of the starting material prior to formation of the pyridine ring:
As be shown in the following reaction formula, 4,6-dichloropicolinic acid lower alkyl ester of the formula (VI) can be synthesized by reacting N-methylpyridonic acid of the formula (VIII) with thionyl chloride to prepare 4,6-dichloropicolinic acid chloride of the formula (VII), followed by reacting the resultant compound of the formula (VII) with lower alkyl alcohol. 
wherein R1 is C1-C4 alkyl group.
(2) Substituted picolinic acid obtained by oxidation of 2-methyl group or 2-hydroxymethyl group on the pyridine ring:
The substituted 2-picolinic acid of the formula (II) can be synthesized by oxidation of a substituted 2-picoline (or substituted 2-pyridine methanol) of the following formula (IX). 
wherein Y and m are each the same definition as described above, and A represents hydrogen atom or hydroxyl group.
(3) Substituted picolinic acid obtained by hydrolysis of cyano group of substituted picolinonitrile:
The substituted picolinic acid of the formula (II) can be synthesized by hydrolyzing a substituted picolinonitrile of the formula (X) according the following reaction formula. 
wherein Y and m means the same definition as described above.
Among the above-described 3 reactions, since the reaction process (1) causes simultaneous chlorination of 4- and 6-positions of the pyridine ring, these chlorine atoms can be utilized as releasable groups in nucleophilic substitution reactions.
As be shown in the following reaction formula, the 4,6-disubstituted picolinic acid lower alkyl ester of the following formula (XI) can be synthesized by nucleophilically substituting chlorine atoms on 4-position and/or 6-position of 4,6-dichloro-picolinic acid lower alkyl ester of the above formula (VI). 
wherein R2 and R3 represent independently chlorine atom, C1-C4 alkoxy group, C1-C4 haloalkoxy group, C1-C4 alkylthio group, C1-C4 haloalkylthio group, amino group, C1-C4 alkylamino group or di-C1-C4 alkylamino group, and R1 represents C1-C4 alkyl group, but R2 and R3 are not chlorine atom at the same time
Among the 4,6-di-substituted picolinic acid lower alkyl ester of the above formula (XI), compounds having a chlorine atom attached to one of 4-position or 6-position, and a C1-C4 alkoxy group, C1-C4 haloalkoxy group, C1-C4 alkylthio group, C1-C4 haloalkylthio group, amino group, C1-C4 alkylamino group or di-C1-C4 alkylamino group attached to the other position can be synthesized by nucleophilic substitution reaction of the chlorine atom on the 4-position or 6-position under the basic condition.
Upon carrying out this nucleophilic substitution reaction, they can be synthesized by selecting the solvent to be used, by which either one of chlorine atoms on 4-position and 6-position causes the nucleophilic substitution under the basic condition.
In addition, compound in which the same or different substituents selected from C1-C4 alkoxy group, C1-C4 haloalkoxy group, C1-C4 alkylthio group, C1-C4 haloalkylthio group, amino group, C1-C4 alkylamino group or di-C1-C4 alkylamino group are attached to both of 4-position and 6-position can be synthesized from the compounds (XI) by nucleophilic substitution reaction of the chlorine atoms on the 4-position and 6-position under the basic condition. In this case, after substitution of one of chlorine atoms on 4-position and 6-position, the other chlorine atom may be substituted, or the both chlorine atoms may be substituted simultaneously.
Among the above reaction processes (1)-(3), the reaction process (2) is suitable for synthesis of substituted picolinic acids in which at least a substituent Y is C1-C4 alkoxy group or C1-C4 haloalkoxy group attached to 5-position.
Compounds of the following formula (XII) having a C1-C4 alkoxy group or C1-C4 haloalkoxy group attached to 5-position can be synthesized, according to the following reaction formula, by converting 5-hydroxyl group of 5-hydroxy-2-picoline of the formula (XIV) to an ether bond by C1-C4 alkylation or C1-C4 haloalkylation to produce 5-substituted-2-picoline of the formula (XIII), followed by converting 2-methyl group into carboxyl group by oxidation. 
wherein R4 represents hydrogen atom, chlorine atom, bromine atom or nitro group, and R5 represents C1-C4 alkyl group or C1-C4 haloalkyl group.
Substituted picolinic acids having a chlorine atom attached to 6 position can be synthesized using 6-chlorinated compound [compound (XIV,R4=Cl)] of 5-hidroxy-2-methylpyridine as the starting material. Further, as shown in the following reaction formula, substituted picolinic acid alkyl ester compounds of the formula (XV) having a C1-C4 alkoxy group or C1-C4 haloalkoxy group attached to 5 position and having a C1-C4 alkoxy group, C1-C4 haloalkoxy group, C1-C4 alkylthio group, C1-C4 haloalkylthio group, amino group, C1-C4 alkylamino group or di-C1-C4 alkylamino attached to 6 position can be derived by nucleophilic substitution reaction of the 6-chlorine atom of 5-substituted-6-chloropicolinic acid lower alkyl ester of the formula (XVI) which was obtained by converting carboxyl group into lower alkyl ester. 
wherein R5 represents C1-C4 alkyl group or C1-C4 haloalkyl group, R6 represents C1-C4 alkoxy group, C1-C4 haloalkoxy group, C1-C4 alkylthio group, C1-C4 haloalkylthio group, amino group, C1-C4 alkylamino group or di-C1-C4 alkylamino group and R1 represents C1-C4 alkyl group.
Upon synthesizing the substituted picolinic acid by oxidation reaction, when pyridine ring has a substituent on 4 position, it is preferred to use a process which comprises synthesizing 2-pyridinemethanol from 2-picoline-N-oxides and oxidizing the formed hydroxymethyl group into carboxyl group as compared with a process which comprises directly converting 2-methyl group on the pyridine ring into carboxyl group by oxidation.
For example, 4-methoxy-6-chloropicolinic acid can be synthesized by oxidation of hydroxymethyl group of 4-methoxy-6-chloro-2-pyridinemethanol, as shown in the following reaction formula. 
The following reaction formula shows a synthetic process of 4-methoxy-6-chloro-2-pyridinemethanol. 
The substituted picolinic acids can be synthesized similarly via hydroxyl group in the case that 4-substituent is halogen atom or nitro group.
Thus resultant substituted picolinic acids may be converted into substituted picolinic acid lower alkyl esters in order to use as starting materials in the nucleophilic substitution reaction for halogen atom or nitro group as the releasable group.
Examples of oxidizing agent used for the above described oxidation reaction include sodium hypochlorite, sodium hypobromide, chlorine, bromine, potassium permanganate, chromic acid and sodium tungstate.
As the reaction solvent, various kinds of solvent, for example, inert solvents such as benzene and chloroform, acetic acid and water, may be used alone or as a mixture thereof.
The reaction temperature is generally 0-100xc2x0 C., preferably 0-60xc2x0 C., and the reaction time is from about 30 minutes to 15 days.
The above-mentioned reaction process (3) is suitable for synthesizing substituted picolinic acids using starting materials having C1-C4 alkyl group and/or C1-C4 haloalkyl group as at least one of substituents Y which is capable of being a reaction site for the oxidation reaction in the reaction process (2).
The following reaction formula shows a process for synthesizing substituted picolinic acids of the formula (XVII) using as the starting material 2-cyano-4-substituted-6-methylpyridine of the formula (XVIII) having methyl group as the C1-C4 alkyl group. 
wherein R7 represents hydrogen atom, halogen atom, nitro group, C1-C4 alkoxy group, C1-C4 haloalkoxy group, C1-C4 alkylthio group, C1-C4 haloalkylthio group, amino group, C1-C4 alkylamino group or di-C1-C4 alkylamino group.
The following reaction formula shows a process for synthesizing substituted picolinic acids of the formula (XXIX) using as the starting material 2-cyano-4-methyl-6-substituted pyridine of the formula (XXVIII) having methyl group as the C1-C4 alkyl group. 
wherein R12 represents hydrogen atom, halogen atom, nitro group, C1-C4 alkoxy group, C1-C4 haloalkoxy group, C1-C4 alkylthio group, C1-C4 haloalkylthio group, amino group, C1-C4 alkylamino group or di-C1-C4 alkylamino group.
The following reaction formula shows a synthetic route of 2-cyano-4-nitro-6-methylpyridine [Compound (XVIII), R7=NO2]
According to the above mentioned reaction formula, 2-picoline-N-oxide is allowed to react with dimethyl sulfate to derive a pyridinium monomethyl sulfate ester salt having methoxy group attached to the nitrogen atom of 1-position, followed by reacting with prussiate such as sodium prussiate to prepare a cyano-ion adduct. The 2-cyano-4-nitro-6-methylpyridine can be prepared by demethanolation of the adduct.
The following reaction formula shows a synthetic route of 2-cyano-substituted pyridines [Compound (XXXII)]. 
wherein Y2 represents halogen atom, C1-C4 alkyl group, C1-C4 haloalkyl group, C1-C4 alkoxy group, C1-C4 haloalkoxy group, (C1-C4 alkoxy) C1-C4 alkyl group or nitro group,
m2is an integer of 0-4, and each Y2 may be identical or different when m2 is 2 or more.
The substituted pyridine-N-oxides [Compound (XXX)] are allowed to react with dimethyl sulfate to introduce into substituted pyridinium monomethyl sulfate ester salts having methoxy group on the nitrogen atom of 1-position [Compound (XXXI)], followed by reacting with prussiate such as sodium prussiate to obtain cyano-ion adducts. 2-Cyano-substituted pyridines [Compound (XXXII)] can be prepared by demethanolation of adducts.
The following reaction formula shows a synthetic route of 2-cyano-5-methoxy-6-methylpyridine using dimethylcarbamoyl chloride and cyanotrimethyl silane. 
2-Cyano-4-substituted-6-methylpyridines of the formula (XIX) which have a C1-C4 alkoxy group, C1-C4 haloalkoxy group, C1-C4 alkylthio group, C1-C4 haloalkylthio group, amino group, C1-C4 alkylamino group or di-C1-C4 alkylamino group on 4-position can be synthesized by nucleophilic substitution reaction of the 4-nitro group of 2-cyano-4-nitro-6-methylpyridine [Compound (XVIII), R7=NO2], as shown in the following reaction formula. 
wherein R8 represents C1-C4 alkoxy group, C1-C4 haloalkoxy group, C1-C4 alkylthio group, C1-C4 haloalkylthio group, amino group, C1-C4 alkylamino group or di-C1-C4 alkylamino group.
2-Cyano-4-methyl-6-substituted-pyridines of the formula (XXVII) which have a C1-C4 alkoxy group, C1-C4 haloalkoxy group, C1-C4 alkylthio group, C1-C4 haloalkylthio group, amino group, C1-C4 alkylamino group or di-C1-C4 alkylamino group on 6-position can be synthesized by nucleophilic substitution reaction of chlorine atom on the 6-position of 2-cyano-4-methyl-6-chloropyridine, as shown in the following reaction formula. 
wherein R11 represents C1-C4 alkoxy group, C1-C4 haloalkoxy group, C1-C4 alkylthio group, C1-C4 haloalkylthio group, amino group, C1-C4 alkylamino group or di-C1-C4 alkylamino group.
As nucleophilic reagents using for the above-mentioned various nucleophilic substitution reaction on the pyridine ring, the following compounds are exemplified.
C1-C4 Alkyl alcohols such as methyl alcohol, ethyl alcohol and 1-methylethyl alcohol in case of introducing C1-C4 alkoxy group such as OCH3, OC2H5 or OCH(CH3)2.
C1-C4 Haloalkyl alcohols such as 2-fluoroethyl alcohol, 2,2-difluoroethyl alcohol, 2,2,2-trifluoroethyl alcohol and 3,3,3-trifluoropropyl alcohol in case of introducing C1-C4 haloalkoxy group such as OCH2CH2F, OCH2CHF2, OCH2CF3 or OCH2CH2CF3.
C1-C4 Alkyl thiols such as methyl thiol in case of introducing C1-C4 alkylthio group such as SCH3.
Ammonia in case of introducing amino group.
C1-C4 Alkyl amines such as methylamine in case of introducing C1-C4 alkylamino group such as NHCH3.
Di-C1-C4 Alkyl amines such as dimethylamine and ethyl methylamine in case of introducing di-C1-C4 alkylamino group such as N(CH3)2 or N(CH3)C2H5.
In case of the nucleophilic substitution reaction on the pyridine ring, it is preferred to carry out the reaction in the presence of a basic compound which captures conjugate acid of the releasable group. When the nucleophilic reagent is a basic compound, it may be used in an excess amount.
Further, the alkyl alcohols or alkyl thiols may be used as a state of sodium alkoxide or sodium thioalkoxide, respectively.
Regarding amounts of compounds used for the nucleophilic substitution reaction, the nucleophilic reagent is used in a range of 0.8-1.2 equivalents and the basic compound is used in a range of 0.8-1.2 equivalent based on 1 mol of the starting material. The reaction may be accelerated by using copper salts such as cuprous iodide together with the basic compound,
The reaction temperature is in a range of xe2x88x9210-80xc2x0 C., and the reaction time is in a range of 30 minutes-5 hours.
The reaction is preferably carried out in an aprotic polar solvent such as N,N-dimethylacetamide or acetonitrile, or ether such as dioxane.
On the other hand, the following processes are adopted in order to produce picolinic acids having substituents which are not suitable for introducing into the pyridine ring by nucleophilic substitution reaction.
A process that the methyl group is oxidized after halogenation of the pyridine ring to synthesize the substituted picolinic acid, in case of the substituents being halogen atom such as Cl or F.
A process that the substituted picolinic acid is synthesized via a step of introducing 2-cyano group after halogenation or nitration the pyridine ring, in case of the substituents being halogen atom such as Cl or F and nitro group.
A process that the substituted picolinic acid is synthesized via a step of introducing 2-cyano group into the pyridine ring to which the substituents are attached, in case of the substituents being C1-C4 alkyl group such as CH3 or CH(CH3)2 or C1-C4 haloalkyl group such as CH2F, CHF2 or CF3.
A process that the substituted picolinic acid is synthesized after the alkyl group of alkyl substituted 2-cyanopyridine is halogenized with N-chlorosuccinimide or N-bromosuccinimide, followed by converting to (C1-C4 alkoxy) C1-C4 alkyl group by alkoxylation or to (C1-C4 alkylthio) C1-C4 alkyl group by alkylthiolation, in case of the substituents being (C1-C4 alkoxy) C1-C4 alkyl group such as CH2OCH3 or (C1-C4 alkylthio) C1-C4 alkyl group such as CH2SCH3.
The substituted picolinic acid phenyl ester of the above formula (IV) can be prepared by synthesizing substituted picolinic acid chloride of the formula (XX) from the substituted picolinic acid of the formula (II), followed by reacting with phenol of the formula (XXI) in the presence of a basic compound, as shown in the following reaction formula. 
wherein Y and m mean each the same definition as described above, Z represents halogen atom, C1-C4 alkyl group, C1-C4 alkoxy group or nitro group, and s is an integer of 0-5, and each z may be identical or different when s is 2 or more.
In general, the compound of the formula (IV) in which the phenyl group in the phenyl ester portion has no substituent is used as the starting materials for production of the compound (I). However, the phenyl group may have the substituents Z.
Specific examples of the substituent Z include fluorine atom, chlorine atom and bromine atom as halogen atom, methyl group as C1-C4 alkyl group, and methoxy group as C1-C4 alkoxy group s is preferably an integer of 0-3.
The substituted picolinic acid chlorides of the formula (XX) can be synthesized by reacting the substituted picolinic acid of the formula (II) with a chlorinating agent such as thionylchloride in an inert solvent such as benzene, chlorobenzene, etc. at a reaction temperature of 20-120xc2x0 C., preferably 80-90xc2x0 C., for a reaction time of 30 minutes-6 hours, preferably 1.5-3 hours.
The substituted picolinic acid phenyl ester of the formula (IV) can be synthesized by reacting the substituted picolinic acid chloride of the formula (XX) with substituted phenol of the formula (XXI) in the presence of a basic compound such as triethylamine, etc. in an inert solvent such as dichloromethane, 1,2-dichloroethane, etc. at a reaction temperature of xe2x88x9210-40xc2x0 C., preferably 20-25xc2x0 C. for a reaction time of 30 minutes-6 hours, preferably 2-3 hours.
Examples of the substituted benzenesulfonamides of the above formula (III) used as the starting material in the production step of N-(phenylsulfonyl) picolinic acid amide derivatives of the formula (I) according to the present invention include the following compounds shown in Table 3.
The compound of the formula (III) can be produced as follows. As be shown in the following reaction formula, the compound of the formula (III) is synthesized by reacting the substituted benzenesulfonyl chloride of the formula (XXII) with ammonia. 
wherein X and n mean the same definitions as described above.
As the substituted benzenesulfonyl chlorides of the above formula (XXII), those available in the market or those prepared by the following process may be used.
In the above reaction, ammonia is used in an amount of about 2-8 times by mol per mol of the compound of the formula (XXII). In general, aqueous ammonia containing 28-30% ammonia is used.
The reaction is carried out by blending a mixture of the compound of the formula (XXII) and an aprotic polar solvent with a mixture of aqueous ammonia and an aprotic polar solvent.
The reaction temperature is in a range of about xe2x88x9220-100xc2x0 C., preferably xe2x88x9210-30xc2x0 C., and the reaction time is about 30 minutes-12 hours.
The substituted benzenesulfonyl chloride of the formula (XXII) can be produced according to the following three kinds of process.
(1) Process for producing the substituted benzenesulfonyl chloride of the formula (XXII) which comprises reacting substituted benzene of the formula (XXIII) with chlorosulfric acid as shown in the following reaction formula: 
wherein X represents halogen atom, C1-C4 alkyl group, C1-C4 haloalkyl group, C1-C4 alkoxy group, C1-C4 haloalkoxy group, (C1-C4 alkoxy)carbonyl group, (di-C1-C4 alkylamino)sulfonyl group, [Nxe2x80x94(C1-C4 alkyl)-Nxe2x80x94(C1-C4 alkoxy)amino]sulfonyl group, (C1-C4 alkylamino)sulfonyl group, a C1-C4 alkylthio group, C1-C4 alkylsulfinyl group, C1-C4 alkylsulfonyl group or nitro group, n is an integer of 0-5, and each X may be identical or different when n is 2 or more.
This process for production is suitable in case of using substituted benzene having halogen atoms, C1-C4 alkyl groups, C1-C4 haloalkyl groups, C1-C4 alkoxy groups, C1-C4 haloalkoxy groups etc. as the substituent X.
In this process, chlorosulfuric acid is used in an amount of about 0.8-3 times by mol per mol of the substituted benzene of the formula (XXIII).
The reaction of this process can be carried out in an inert solvent such as carbon disulfide, chloroform, carbon tetrachloride, tetrachloroethane, etc. The reaction temperature is in a range of about 0-200xc2x0 C., and preferably about 20-120xc2x0 C. The reaction time is about 20 minutes-few days.
(2) Process for producing substituted benzenesulfonyl chloride of the formula (XXII) which comprises synthesizing the substituted benzenediazonium chloride of the formula (XXIV) from substituted aniline of the formula (XXV), followed by reacting the compound of the formula (XXIV) with sulfur dioxide in the presence of cuprous chloride: 
wherein X and n mean each the same definition as described above.
This process for production is suitable in case of using substituted aniline having halogen atoms, C1-C4 alkyl groups, C1-C4 haloalkyl groups, C1-C4 alkoxy groups, C1-C4 haloalkoxy groups, (C1-C4 alkoxy)carbonyl groups, (di-C1-C4 alkylamino)sulfonyl groups, [Nxe2x80x94(C1-C4 alkyl)-Nxe2x80x94(C1-C4 alkoxy )amino]sulfonyl groups, (C1-C4 alkylamino)sulfonyl groups, C1-C4 alkylthio groups, C1-C4 alkylsulfonyl groups, etc. as the substituent X.
The diazotization reaction of substituted anilines of the above formula (XXV) or salts thereof can be carried out under conventional conditions, for example, by reacting with sodium nitrite in hydrochloric acid under cooling to xe2x88x9220-10xc2x0 C., by which the substituted benzenediazonium chloride of the above formula (XXIV) is synthesized. This substituted benzenediazonium chloride is then allowed to react with sulfur dioxide in the presence of cuprous chloride to produce the substituted benzenesulfonyl chloride of the above formula (XXII).
Amounts of each reagent used for synthesis of the substituted benzenediazonium chloride of the formula (XXIV) are as follows.
The amount of sodium nitrite used is about 1.2 times by mol per mol of substituted aniline of the formula (XXV) or salt thereof.
The amount of hydrochloric acid used is usually 2.5-6 times by mol per mol of substituted aniline of the formula (XXV) or salt thereof. Aqueous solution of 35% concentration is preferably used.
Lower alkanoic acid such as acetic acid or propionic acid may be used as a reaction solvent together with aqueous hydrochloric acid.
Amounts of each reagent used for synthesis of the substituted benzenesulfonyl chloride of the formula (XXII) are as follows.
Cuprous chloride is used in a range of about 0.01-3 times by mol and sulfur dioxide is used in a range of about 0.8-8 times by mol, per mol of substituted benzenediazonium chloride of the formula (XXIV), but the sulfur dioxide may be used in a large excess amount.
The sulfur dioxide may be introduced as a gas from a gas cylinder, or it may be prepared by mixing sodium hydrogen sulfite with aqueous hydrochloric acid. In such a case, lower alkanoic acid such as acetic acid or propionic acid may be used as a reaction solvent.
Accordingly, in case of conducting the reaction, it is possible to use lower alkanoic acid absorbing the sulfur dioxide gas may be used, or to use a lower alkanoic acid mixture which is prepared by adding aqueous hydrochloric acid to lower alkanoic acid containing sodium hydrogen sulfite at xe2x88x9210-5xc2x0 C. so that sulfur dioxide is generated. In the latter case, 0.8-1.4 times by mol of hydrochloric acid are usually used per mol of sodium hydrogen sulfite in order to generate sulfur dioxide.
The reaction of synthesizing the substituted benzenesulfonyl chloride of the above formula (XXII) by reacting substituted benzenediazonium chloride with sulfur dioxide in the presence of cuprous chloride is conducted under acidic conditions. The reaction temperature is in a range of about xe2x88x9220-100xc2x0 C., preferably xe2x88x9210-30xc2x0 C. The reaction time is in a range of from 30 minutes to 12 hours or so.
(3) Process for producing the substituted benzenesulfonyl chloride of the formula (XXII) which comprises oxidatively chlorinating the 2-valent sulfur substituent of substituted benzene sulfide of the formula (XXVI) with a chlorinating agent in the presence of water as shown in the following reaction formula: 
wherein X and n mean each the same definition as described above, and R9 represents hydrogen atom, benzyl group, or phenylthio group having substituents Xn on the benzene ring.
This process for production is suitable in case of using substituted benzene sulfide having substituents such as halogen atom, C1-C4 alkyl group, C1-C4 haloalkyl group, C1-C4 alkoxy group, C1-C4 haloalkoxy group, (C1-C4 alkoxy)carbonyl group, (di-C1-C4 alkylamino)sulfonyl group, [Nxe2x80x94(C1-C4 alkyl)-Nxe2x80x94(C1-C4 alkoxy)-amino]sulfonyl group, (C1-C4 alkylamino)sulfonyl group, nitro group etc. as the substituent X.
This process is carried out oxidatively chlorinating the 2-valent sulfur substituent of the substituted benzene sulfide of the above formula (XXVI) in the presence of water to derive substituted benzenesulfonyl chloride of the formula (XXII).
Chlorine, sodium hypochlorite, potassium hypochlorite, N-chlorosuccinimide, etc. are used as the chlorinating agent. The chlorinating agent is used in a range of from about 1 to 10 times by mol per mol of the starting compound.
This reaction is preferred to conduct under acidic conditions by adding hydrochloric acid, acetic acid, etc. The reaction temperature is in a range of from about xe2x88x9210 to 30xc2x0 C. and the reaction time is in a range of from 30 minutes to 5 hours or so.
Substituted benzenesulfonamides having a C1-C4 alkylsulfinyl group or C1-C4 alkylsulfonyl group of the formula (III-a) can be synthesized by oxidizing a C1-C4 alkylthio group of the substituted benzenesulfonamide having the C1-C4 alkylthio group of the formula (III-b) as shown in the following reaction formula. 
wherein R10 represents C1-C4 alkyl group and r is 1 or 2.
Benzenesulfonamides having a C1-C4 alkylsulfonyl group can be prepared as shown in the following reaction formula which comprises protecting amino group of aniline having a C1-C4 alkylthio group, oxidizing the C1-C4 alkylthio group into a C1-C4 alkylsulfonyl group, separating the acetyl group to return to amino group, and converting the amino group into a sulfamoyl group by reactions of synthesizing the compound of the formula (XXII) from the compound of the above formula (XXV) via the compound of the formula (XXIV) or reactions of synthesizing the compound of the formula (III) from the compound of the formula (XXII). 
wherein R10 represents C1-C4 alkyl group.
Examples of the oxidizing agents used for the above described oxidation reaction include peracids, sodium hypochlorite, chlorine, potassium permanganate and sodium tungstate. Examples of preferable peracids include acetic peracid, benzoic peracid, metachlorobenzoic peracid and phthalic peracid. In case of using acetic peracid, it may be formed during the oxidation step from acetic acid and aqueous hydrogen peroxide.
As the reaction solvent, various kinds of solvent such as inert solvent such as chloroform, and acetic acid, water, etc. can be used alone or as a mixture thereof.
The reaction temperature is usually in a range of about 0 to 100xc2x0 C., preferably 10-60xc2x0 C. and the reaction time is in a range of 3 hours to 15 days or so.
For example, the compound can be used as a starting material of the present invention by converting 2-SCH3 into 2-SOCH3 or 2-SO2CH3 by oxidation.
The process of conversion of the thio bond to the sulfuryl bond or sulfonyl bond by oxidation can be utilized not only for production of substituted benzenesulfonamide of the formula (III) having a plurality of C1-C4 alkylthio groups as the substituents Xn but also for production of substituted benzenesulfonamide of the formula (III) having substituents other than C1-C4 alkylthio groups.
Furthermore, it can be utilized as a process for converting the C1-C4 alkylthio group in the N-(phenylsulfonyl)picolinic acid amide derivatives of the formula (I) having at least one C1-C4 alkylthio group into a C1-C4 alkylsulfonyl group or a C1-C4 alkylsulfinyl group.
The N-(phenylsulfonyl)picolinamide derivatives of the above formula (I) has a 2-substituted carbamoyl group attached to the pyridine ring and an N-substituted sulfamoyl group attached to the benzene ring.
Replacing hydrogen atoms on the nitrogen atoms of the 2-substituted carbamoyl group and the 2-substituted sulfamoyl group by suitable cations can produce salts. These salts are generally metal salts, particularly alkali metal salts or alkaline earth metal salts or, sometimes, alkylated ammonium salts or organic amine salts, which may be produced in a solvent such as water, methanol or acetone at a temperature of 20-100xc2x0 C. In the present invention, examples of suitable bases for producing salts include alkali metal carbonates, alkaline earth metal carbonates, ammonia and ethanolamine.
The N-(phenylsulfonyl)picolinamide derivatives of the above formula (I) according to the present invention exhibit reliable herbicidal activity at low application dosages and show selectivity between crops and weeds. The herbicides containing these compounds as an active ingredient are therefore suitable for controlling either before or after emergence monocotyledonous weeds and dicotyledonous weeds in important crops such as wheat, rice, corn, soybean, etc.
Exemplary dicotyledonous weeds which can be controlled by the herbicides of the present invention include Amaranthus, Bidens, Stellaria, Abutilon, Convolvulus, Matricaria, Galium, etc.
Exemplary monocotyledonous weeds include Echinochloa, Setaria, Digitaria, Avena, Cyperus, etc.
The applicable places of the herbicides according to the present invention range from agricultural lands such as upland fields, paddy fields, orchard, etc. to non-agricultural lands such as athletic fields, factory sites, etc.
Although the compounds of the present invention may be used alone, they are generally used as various preparation forms such as powder, wettable powder, granule, emulsion, etc. together with preparation aids.
Preparation is carried out such a manner that one or more of the compounds according to the present invention are contained in the composition in an amount of 0.1-95% by weight, preferably 0.5-90% by weight and more preferably 2-70% by weight.
In exemplifying carriers, diluents and surfactants used as the preparation aids, examples of solid carrier include talc, kaolin, bentonite, diatom earth, white carbon, clay, etc. Examples of liquid diluents include water, xylene, toluene, chlorobenzene, cyclohexane, cyclohexanone, methylsulfoxide, N,N-dimethylformamide, ethyl alcohol, 1-methylethyl alcohol, etc.
The surfactants are used according to their effect. Examples of emulsifiers include polyoxyethylene alkylaryl ether, polyoxyethylene sorbitan monolaurate, etc. Examples of dispersing agents include lignin sulfonate, dibutylnaphthalene sulfonate, etc. Examples of wetting agents include alkylsulfonate, alkylphenylsulfonate, etc.
The above preparation herbicides are divided into those which are be used intact and those which are used by diluting with a diluent such as water to a desired concentration. In case of the preparation herbicides using by dilution, it is preferable that the compound of the present invention is in a range of 0.001-1.0%.
The application dosage of the compound according to the present invention is 0.01-10 kg and preferably 0.05-5 kg per ha.
Since the concentration and the application dosage depend on type of formulations, application term, method of application, place to be applied and crops to be applied, they can be varied of course irrespective of the above-described ranges. Moreover, the compound of the present invention may be used together with other active ingredients such as fungicides, insecticides, miticides, and herbicides.